Question

6. Red-green color blindness occurs in about 8% of males and .4% of females. Many genes contribute to Red-green colorblindness and most of these are sex-linked, which is the reason for the disparity in the frequency between males and females. Call the allele that encodes a functional product "+" and the allele that encodes a non-functional product "=". Why is Red-green color blindness more fequent in males?

a.   because males inherit only a single X chromosome, which means that inheriting only a single copy of the "-" allele is sufficient to have the condition
b. because males inherit a Y chromosome, which is much more likely to contain the "-" allele than is the X chromosome

c. because males inherit two copies of the X chromosome, and so have twice the likelihood of inheriting the "-" allele in one of the genes.

d. because females inherit a Y chromosome, which rarely contains the "-" allele

e. e. because females inherit two Y chromosomes, and so need to inherit two copies of the "-" allele to have the condition

7. let's say ATP1A1 (encoding the Na+/K+ ATPase) has two alleles: + (which encodes a functional product) and - (which encodes a non-functional product). A person who inherits the +/- genotype

a. makes 50% functional Na+/K+ ATPase in every cell, because both + and - copies are present in each cell

b. makes 100% functional Na+/K+ ATPase, because one only copy of the + allele is necessary to make 100% functional product

c. makes 0% functional Na+/K+ ATPase, because two copies of the + allele are necessary to make a functional product

d. makes 100% functional Na+/K+ ATPase in cells with the + copy and 0% functional Na+/K+ ATPase in cells with the - version

            e. makes a Na+/K+ ATPase molecule that pumps Na+ but not K+

8. Lets say LDLR (encoding the LDL-receptor) has two alleles: + (which encodes a functional product) and - (which encodes a non-functional product). LDL receptor transports LDL from the blood into tissue cells and is necessary for normal lipid homeostasis. LDLR is on chromosome 19. A person with either the +/- or -/- genotype has familial hypercholesterolemia. Which of the following is true?

                a. familial hypercholesterolemia is autosomal dominant because the "-" allele causes the disease

b. familial hypercholesterolemia is autosomal recessive because a single copy of the "-" allele is sufficient to express the phenotype

c. familial hypercholesterolemia is autosomal dominant because the "-" allele is the most common in the population

d. familial hypercholesterolemia is autosomal recessive because it is the "-" allele that causes the disease

e. familial hypercholesterolemia is autosomal dominant, because a single copy of the "-" allele is sufficient to express the phenotype

9. Jack and Jill went up the hill to mate. Jack is +/+ at the CFTR locus. Jill is +/- at the CFTR locus. Which of the following statements is TRUE?

Background: The CFTR gene encodes a Cl- channel. Cystic fibrosis (CF) is an autosomal recessive disease arising because of mutations of the CFTR gene that result in alleles ("-") that produce a non-functional Cl- channel.

                a. 100% of their children are expected to have CF

                b. 0% of their children are expected to have CF

                c. 50% of their children are expected to have CF

                d. 25% of their children are expected to have CF

                e. 75% of their children are expected to have CF

Answer 1

6. A. because males inherit only a single X chromosome, which means that inheriting only a single copy of the "-" allele is sufficient to have the condition.

7. c. makes 0% functional Na+/K+ ATPase, because two copies of the + allele are necessary to make a functional product.

8. e. familial hypercholesterolemia is autosomal dominant, because a single copy of the "-" allele is sufficient to express the phenotype

9. b. 0% of their children are expected to have CF.